Menu
I want to save a Swift Style String Array into NSUserDefaults, but acutally the "if" statement in the code says that returnValue is always nil.
Later in the code (iOS 8) I want to use "food += ["spaghetti"] to add new entries.
var food : [String] {
get {
var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
if returnValue == nil //Check for first run of app
{
returnValue = ["muesli", "banana"]; //Default value
}
return returnValue!
}
set (newValue) {
NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
NSUserDefaults.standardUserDefaults().synchronize()
}
}
232
To store the string in the user's defaults database, which is nothing more than a property list or plist, we pass the string to the set(_:forKey:) method of the UserDefaults class. We also need to pass a key as the second argument to the set(_:forKey:) method because we are creating a key-value pair.
Storing Default Objects The NSUserDefaults class provides convenience methods for accessing common types such as floats, doubles, integers, Boolean values, and URLs. These methods are described in Setting Default Values.
The NSUserDefaults class is thread-safe.
static func setObject(value:AnyObject ,key:String) { let pref = NSUserDefaults. standardUserDefaults() pref. setObject(value, forKey: key) pref. synchronize() } static func getObject(key:String) -> AnyObject { let pref = NSUserDefaults.
There are several convenience methods for storing data in NSUserDefaults they include: Reading is done in a very similar fashion. You need to get a reference to the NSUserDefaults object, and then ask it for the value you want. In the case of reading out the String we wrote in and printing it to the console, we would use the code:
[ [NSUserDefaults standardUserDefaults] setObject:@"Netherlands" forKey:@"HomeCountry"]; To save custom objects into the `NSUserDefaults` you need to make your CustomClass confirm to protocol of `NSCoding`.
An interface to the user’s defaults database, where you store key-value pairs persistently across launches of your app. The NSUserDefaults class provides a programmatic interface for interacting with the defaults system.
The NSUserDefaults class provides a programmatic interface for interacting with the defaults system. The defaults system allows an app to customize its behavior to match a user’s preferences.
The following code should help you resolve your problem:
import UIKit
class ViewController: UIViewController {
var food: [String] {
get {
if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
return returnValue
} else {
return ["muesli", "banana"] //Default value
}
}
set {
NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
NSUserDefaults.standardUserDefaults().synchronize()
}
}
override func viewDidLoad() {
super.viewDidLoad()
print(food) // prints: ["muesli", "banana"] (at first launch)
food = ["cake"]
print(food) // prints: ["cake"]
food += ["spaghetti"]
print(food) // prints: ["cake", "spaghetti"]
food = []
print(food) // prints: []
NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
print(food) // prints: ["muesli", "banana"]
}
}
However, with the previous code, if you set food = [], you will have a problem as food won't return ["muesli", "banana"]. In order to avoid this, you may prefer the following code:
import UIKit
class ViewController: UIViewController {
var food: [String] {
get {
if let returnValue = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String] {
return returnValue == [] ? ["muesli", "banana"] : returnValue
} else {
return ["muesli", "banana"] //Default value
}
}
set {
NSUserDefaults.standardUserDefaults().setObject(newValue, forKey: "food")
NSUserDefaults.standardUserDefaults().synchronize()
}
}
override func viewDidLoad() {
super.viewDidLoad()
print(food) // prints: ["muesli", "banana"] (at first launch)
food = ["cake"]
print(food) // prints: ["cake"]
food += ["spaghetti"]
print(food) // prints: ["cake", "spaghetti"]
food = []
print(food) // prints: ["muesli", "banana"]
NSUserDefaults.standardUserDefaults().setObject(nil, forKey: "food")
print(food) // prints: ["muesli", "banana"]
}
}
As stated in the documentation:
For NSArray and NSDictionary objects, their contents must be property list objects.
This means you need to convert your String objects to NSString when saving, something like this should work:
var food : [String] {
get {
var returnValue : [String]? = NSUserDefaults.standardUserDefaults().objectForKey("food") as? [String]
if returnValue == nil //Check for first run of app
{
returnValue = ["muesli", "banana"]; //Default value
}
return returnValue!
}
set (newValue) {
// Each item in newValue is now a NSString
let val = newValue as [NSString]
NSUserDefaults.standardUserDefaults().setObject(val, forKey: "food")
NSUserDefaults.standardUserDefaults().synchronize()
}
}
In Swift 3.0
Store
UserDefaults.standard.set(newValue, forKey: "yourkey")
UserDefaults.standard.synchronize()
Retrieve
var returnValue: [NSString]? = UserDefaults.standard.object(forKey: "yourkey") as? [NSString]
Remove
UserDefaults.standard.removeObject(forKey: "yourkey")
Reference: NSUserdefault objectTypes
9
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
